1. Field of the Invention
Embodiments of the invention are directed to sending a reduced representation of logging data from a repository to a log analysis application.
2. Background of the Invention
Modern petroleum drilling and production operations demand a great quantity of information relating to parameters and conditions downhole. Such information may comprise characteristics of the earth formations traversed by the borehole, along with data relating to the size and configuration of the borehole itself. The collection of information relating to conditions downhole, which may be referred to as “logging,” can be performed by several methods.
FIG. 1 illustrates a wireline logging system 100. The system 100 comprises a logging device 102 disposed in a borehole 104 that contains drilling fluid 106. The borehole 104 penetrates a formation 108, which may comprise several distinct layers of the underlying formation. The logging device 102 is connected by a wireline cable 110 to a well-logging truck 112 located at the surface. The wireline cable 110 provides power to the logging device 102 and is used to transmit signals from the logging device 102 to the well-logging truck 112. The well-logging truck 112 contains a collection system 114 that receives the signals, converts the signals into logging data, and stores the logging data in storage 116. After being stored in the storage 116, the logging data may be sent to a repository.
An alternative method of logging is the collection of data during the drilling process. Collecting data during the drilling process eliminates the necessity of removing the drilling assembly to insert a wireline logging device. Designs for measuring conditions downhole, including the movement and location of the drilling assembly contemporaneously with the drilling of the well, have come to be known as “measurement-while-drilling” techniques, or “MWD”. Similar techniques, concentrating more on the measurement of formation properties, have been referred to as “logging while drilling” techniques, or “LWD”. While distinctions between MWD and LWD may exist, the terms MWD and LWD often are used interchangeably. For the purposes of this disclosure, the term LWD will be used with the understanding that this term encompasses both the collection of formation properties and the collection of information relating to the movement and position of the drilling assembly.
In both LWD and wireline logging, the logging data obtained from a logging device may be transferred to the surface and eventually finds its way to a data repository, such as a database. The repository stores the logging data and handles requests for accessing the logging data by applications or programs designed to aid in interpreting the log data, some of which may be web-based. Geologists may use the programs to view the measurements obtained from the logging device.
The repository may store each datum of the logging data as a pair of floating point numbers. For each datum, a first floating point number may represent the value of the formation (e.g., resistivity or conductivity) and/or borehole characteristic measured, and a second floating point number may represent the associated depth. Thus, when requesting logging data from the repository, two floating point numbers may be sent for each datum. The time required to transfer logging data from the repository, especially over serial communication channels such as a standard 28.8 Kbps (kilo-bit per second) modem, may take from several minutes to several hours.
Thus, efficient mechanisms for transferring measurements from a data repository are desirable.